A university worker stabbed his boss 15 times and wrote "bully" across her forehead after becoming obsessed with her, a court heard.

David Browning left Jillian Howell lying covered in blood on the floor of her lounge after attacking her repeatedly with a knife in the chest, neck and abdomen, Hove Crown Court heard on Monday.

Undated handout file photo issued by Sussex Police of Jillian Howell, as university staff member David Browning is set to stand trial accused of murdering Ms Howell, who was his boss.

He stayed in the house for "several hours" before dialling 999 at around 6am on October 26 last year to say he was standing outside a police station and had tried to kill himself. When he was approached by officers, he was found to have a gun and knife but was "calm, coherent and collected".

When asked what happened, he said: "In a nutshell, I have killed my boss," the court heard.

The 52-year-old is standing trial accused of murdering the Samaritans volunteer, who was his superior in the University of Brighton payroll department, after he formed an "intense attachment" towards her and became "possessive, controlling and jealous".

After contacting police, Browning directed officers to Ms Howell's home in Sandgate Road, Brighton. They found her body inside with the word bully "scrawled" across her forehead and graffiti scribbled across the walls, prosecutor Alan Gardner said.

The married father-of-two admits manslaughter by diminished responsibility and possession of a knife in a public place, claiming his actions were prompted by depression brought on by the death of his father a year earlier. He denies murder.

Mr Gardner told the court Browning had worked in the payroll department since 1989 and first met Ms Howell when she joined as a manager in 2015.

He was her deputy and at times "expressed unhappiness" at her management style but the pair became friends and started seeing each other socially outside of work from June last year, the court heard.

Ms Howell told friends she was trying to "cheer up" a colleague by inviting him around for dinner and hoped her experience working with the suicide support charity would help.

In a string of text messages read to the court, Browning described her in one as "stunning" and in another said: "I adore you personally and professionally".

In another he asked to see her again in September or October, adding: "I think you will realise how much you mean to me as a friend".

Later he sent her a message which said: "You are more than just my boss and I think you know that."

She told a friend she had sought professional help for Browning after he demanded she "must never leave the university or get a boyfriend as he needed her support", Mr Gardner said.

He attended three sessions with the university's occupational health team but "blamed" Ms Howell after describing these as making him realise he was "f*****" and "much worse" than he thought.

Browning, of Willow Drive in Seaford, East Sussex, claimed he suffered an "abnormality of function" during the killing but Mr Gardner branded it a "premeditated, cold-blooded murder of a woman in her own home by a colleague she trusted".

The court heard Browning plotted the murder for at least a month, having applied for a shotgun licence and buying the weapon, allegedly telling shop staff he was taking up clay pigeon shooting.

Later, he bought a hunting knife with a 10cm blade - which was found to have been used in the killing - and said he needed it for outdoor sports.

Jurors were also told he picked up a hire van the day before which he drove to Ms Howell's house, leaving the shotgun inside.

Graffiti Browning allegedly wrote on the walls of her home even tried to implicate her close friend Sean McDonald - a former Worthing mayor - in the death but the court heard he was not involved.

Mr Gardner called it a "carefully planned murder out of jealously and out of anger" because Browning feared she was about to reject him.

He added: "He went to her house with the intention to kill her and also, he says, with the intention to kill himself. At some point during the course of that meeting he attacked her [and] stabbed her in the back.

"He didn't want anyone else to know about his problems. He had grown attached to her."